Beginner's guide to using a DSLR camera and/or GoPro for taking star trail photographs

 The Weather has been pants hasn't it. Everytime there has been a clear night recently, it has always coincided with a full moon; or I have had other pressing family commitments and so haven't been able to get out at night. 

So I am severely curtailing my ambitions for my landscape astrophotography over the next few months. What I would like to walk away with at the end of October is the following:

• a circular star trail landscape photograph of my local church
• similar photo of Windy Cross (A Granite cross and little leat waterfall) on Dartmoor 
• a star trail photo of Rame Head chapel

On the milky way landscape photo front, my ambitions are to obtain by end of October:

• Dartmouth Day mark 
• Start Point Lighthouse
• Rame Head chapel
• Wembury Church
• The Great Mewstone at Wembury Point 
• a better image of Bigbury Island under the milky way alongside one of the huge beach tractor as well

So, to the focus of this blog post. Star trails on a DSLR and/or GoPro. 

Funds are tight. I cannot afford another DSLR body at the moment. My two other cameras are a GoPro Hero 9 and a Sony HX-90 digital compact.  I think the trails will be easier to do on the GoPro, but I am open to that belief being challenged. 

Copyright: Wheal Owles by Simon Torr

So, here are my tips for using your DSLR to gain star trail images:

*source of some information: Peter Zelinka Star Trails tutorial

** I haven't yet shot any star trail images so these are my PLANNED INTENDED settings for future shoots 

Firstly equipment! You will need:

• DSLR
• dummy battery and power bank OR several spare batteries
• Stable tripod with good ball head
• Intervalometer
• wide angle lens - in my case my samyang 14mm. If you want curves - try a 24mm lens, for lines, try 50mm
• Fast SD card - you will need a class 10 UHS class 3 memory card, minimum 32gb - better 64gb

Secondly, what settings do we use? 

1. apply the 300 rule and go for 90% sky coverage in your landscape photo 
2. do one foreground shot at the start or end of your session - so that you can merge it with your stacked star trails in post editing
3. settings:  ISO 1600+ to get lots of stars and dense bright trails; ISO 100 - 800 to get fewer stars and bigger gaps between individual trails with better star colours. In an urban sky - try ISO 400 to 800 at F/4 to F/5.6
4. If light conditions are too bright - reduce ISO and open up the aperture - try F/4
5. shutter speeds - 20 to 30". However, if you use a very low ISO you can increase your shutter speed to 60", 120" or even 180", capturing more light, a cleaner image with less noise and grain. 
6. White balance 3000 - 5200K. I will be probably starting at 3600K. Don't use 'auto'
7. LNR off
8. use an intervalometer. Here it gets tricky. You will either use a 1" delay between your shots or the length of your shutter speed + 1" more. And you need to experiment first before you go out for the night. Peter Zelinka's tutorial really explains it well and you can access it here https://www.peterzelinka.com/startrails
9. I set my intervalometer to take around 3 hrs worth of shots minimum, but that's just me. 
10. set your DSLR to evaluative metering
11. Direction - face north = circles; S = downward arcs; E or W = upward arcs

So what about settings for your GoPro? Mine is a Hero 9

• Night Lapse mode
• FOV - wide
• shutter speed 30" - if in urban environments - then shorten it
• Interval - auto
• ISO 100 - 200 (or 100 min to 800 max)
• If using Protunes - Flat colour and WB of 4000 - 5500K
• shoot in RAW images
• collect 3 - 5 hrs worth of images

Equipment: 

• stable tripod
• spare batteries and/or powerbank and cable
• GoPro camera

Above is an outline of how I go about getting my star trail images. The next step is how to post edit them ad for that I use a program called Starstax.  Having not yet taken any star trails, I won't go into using StarStax until I have used it myself. 

Imaging IC1396 and the Elephant Trunk's nebula.

 This is my first attempt at IC 1396, a large emission nebula which is a region of ionized gas that glows due to the energy from nearby stars, particularly a very bright, massive star (HD 206267).

It is two nights worth of data as outlined below taken over two nights when there was a full moon, so to be honest I am pleasantly surprised that anything showed up at all!

IC 1396 has a magnitude of 3.5 and is in the constellation Cepheus, approximately 2,400 light-years away from Earth; a vast and complex area. Its most prominent feature is the Elephant's Trunk Nebula (IC1396A), a concentration of interstellar gas and dust forming a dark, finger-like structure. The entire IC1396 nebula spans over 3 degrees and has a near hollow and gas-poor interior and a complex of dark nebulae threaded throughout the perimeter. Many of the dust structures are aligned so they appear to radiate away from the stars in the nebula’s core.

Look for the reddish star which is Mu Cephei, also known as Herschel’s Garnet Star. The tenth brightest star in the constellation Cepheus, with an average apparent brightness of 4.08, it has a radius 1,260–1,650 times that of the Sun and is one of the biggest stars ever discovered; situated at a distance of about 2,840 light-years from Earth.

IC 1396A, better known as the Elephant Trunk Nebula, is a dark nebula formed by an irregular pillar of dust many light-years long. Pressure from bright stars in the core blows dust from that area leaving behind a darker region at the centre of the nebula while compressing dust around the edges, which drives new star formation. As a result, up to 250 young stars- all less than 100,000 years old, have been detected in infrared images taken of the Trunk region. The Trunk itself is about 20 light-years long. It is the first image in which I have ever captured a strong star formation area of the heavens above.

Imaging equipment used:  Canon 800D DSLR, Zenithstar 61ii refractor scope, EQM-35-Pro mount and guiding with ASIair mini, RVO 32mm guide scope and ZWO 120mm mini guide cam.

Data acquisition: two nights of same data collection – ISO1600, lights 25 x 300”, 10 darks, 10 biases and 15 flat frames. Full moon at 96%+ on each night. Location – two different sites in Cornwall.

So, what do I think about the images?

They were quite hard to process. I use SIRIL, GraXpert and Affinity Photo and somewhere along the way I tend to over saturate the colours and incorrectly process the background sky. I have overstretched the images resulting in star over-bloating as well. So, these are very much a first effort.

Am I pleased with them? Yes. Sort of. I am pleased I captured the data on very bright moonlit nights from two separate locations. The post editing? Well, as always, it is a work in progress isn’t it. 

Report card?  Considerable effort, showing some good acquisition skills but clearly more focus required in post editing! B+

These are the minimally processed first effort images 

First effort 'over-cooked' images

So a third effort will be necessary over the next few days

What do you think I could do to improve the processing further? Let me know in the comment box below. Thanks 

My most recent re-edits.....progress is slow! 😅

IC 1318 The Sadr region

 The Sadr region, known as IC 1318 or the Gamma Cygni Nebula, is a diffuse emission nebula that surrounds the star Sadr.  Around 5000 light years away from Earth, the area also includes the Crescent Nebula (NGC 6888) and The Butterfly Nebula as well - which is really IC 1318. You can see a dark thin dust alley and then two glowing cosmic wings either side of it - hence 'The butterfly'. 

The nebulas glow comes from nearby stars releasing streams of charged particles known as stellar winds; these ionise the gases causing them to emit light. 

Sadr is a yellow-white supergiant with x12 the mass of our sun and x 150 its radius. It lies at the centre of this stunning Hydrogen II emission region. 

So, acquisition details? 

This is the result of two nights worth of data, processed in SIRIL and Affinity Photo. 

Equipment used: 

• Astro-modded Canon 800D
• Samyang 135mm F/2.8 lens
• EQM-35-Pro mount
• ASIair mini with RVO 32mm guide scope and ZWO 120mm mini guide cam
• Optolong L-enHance filter clip in eos

Acquisition times:  on each night 

• 35 x 240" subs
• 10 darks
• 10 biases
• 20 flats 

I find post editing difficult. There is so much to learn and I am never sure whether I am getting the final image right in terms of tone and look at the end of it all! 

But, here are my three attempts thus far in the order I did them: 

So, this one is fairly good. I like it but I felt I could have done a slightly more aggressive black point adjustment to get the background sky darker; taking care not to blow out the stars

😧From one extreme to another. Second go and I overcooked it - too much saturation, vibrance and contrast. Back to the drawing board! 

And my third effort - a halfway house. Better sky, better colours, not oversaturated but lost the stars! 

Have I ever told you this post editing alarkey is hard work?